Friction stir welding apparatus and method and processing apparatus and method

ABSTRACT

The invention provides a friction stir welding apparatus and method and a processing apparatus and method, which are not easily affected by deformations of a work being processed. The friction stir welding apparatus inserts a rotating tool into the work and moves the rotating tool relative to the work to join members of the work. The friction stir welding apparatus and method and the processing apparatus and method of the invention, the latter cutting or grinding the work with a rotating cutter or grindstone, comprises controlling a relative distance between the tool, cutter or grindstone and the work under the joining or processing operation or an insertion depth so that the load factor or electric current of a spindle motor for rotating the tool, cutter or grindstone is within a predetermined range, and a controller therefor.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a novel friction stir weldingapparatus and method and a novel processing apparatus and method, bothof which keep constant a relative distance between a tool, cutter orgrindstone and a work to be welded or processed during friction stirwelding, cutting or grinding.

[0002] The friction stir welding is a method that can join members of awork of such materials as aluminum and aluminum alloys (simply referredto as aluminum hereinafter), magnesium and magnesium alloys (simplyreferred to as magnesium hereinafter), copper and copper alloys (simplyreferred to as copper hereinafter), titanium and titanium alloys (simplyreferred to as titanium hereinafter), and iron or steel (simply referredto as iron hereinafter) in solid phase at temperatures below theirmelting points. More specifically, this is the method of inserting atool, essentially harder than the work to be welded, into the work whilerotating the tool, and moving the rotating tool relative to the work toutilize frictional heat generated between the tool and the work as wellas a resulting plastic flow and join members of the work together. Thismethod has been known by JP-07-505090A. That is, the method takesadvantage of a plastic flow caused by frictional heat between the tooland the work and, unlike conventional welding such as arc welding andelectron beam welding, does not melt the work during the process ofwelding.

[0003] Further, unlike the conventional friction welding method in whichmembers to be processed are rotated against each other and joinedtogether by frictional heat produced by the relative rotation, thefriction stir welding method can continuously join the members of thework along a joint line longitudinally at a temperature below themelting point of the material. The joint line may be not only a straightline but also a curve or a three-dimensional curve.

[0004]FIG. 2 is a sectional view schematically showing a joining statein the friction stir welding. A hard tool 10 comprising a shoulder 11and a pin 12 is rotated by a spindle motor not shown. A revolutionspeed, which depends on the material and shape of the work to be joined,is set at around 1,000 rpm. The tool 10 is then inserted into the work apredetermined depth from the surface 13 of the work and is movedrelative to the work in a direction of joint 14. A speed of movement,which also depends on the material of the work to be joined, is about500 mm/min. It is noted here that the tool 10 is tilted at apredetermined angle θ to the work toward the rear side with respect tothe direction of movement. In the friction stir welding, the quality ofjoint is affected by the shape of the tool, the revolution speed, thespeed of tool movement, and others. It is current practice that thesefactors are optimized based on user's knowhow. The most important oneamong the factors to be optimized is a distance or depth by which thetool 10 is inserted into the work.

[0005]FIG. 3 is a sectional view schematically showing a joining statein the friction stir welding when the distance for which the tool 10 isinserted into the work is set slightly deeper as compared with that ofFIG. 2. The insertion depth of the tool 10 in the range between those ofFIG. 2 and FIG. 3 results in a satisfactory joint quality. When thedepth of insertion of the tool 10 into the work is set larger than thatof FIG. 3, the shoulder 11 on the moving direction 14 side of the tool10 sinks into the surface 13 of the work, thereby cutting the work withthe side surface of the tool 10. In this case, the surface 13 of thatportion of the work which has undergone the joining operation isrecessed significantly from the remaining portion, and the materialexcessively cut off is discharged outside as burrs. Conversely, when thedepth of insertion of the tool 10 into the work is set smaller than thatof FIG. 2, the shoulder 11 on the side opposite the moving direction 14of the tool 10 parts from the surface 13 of the work, reducing theeffect of holding down the material stirred by the pin 12, with theresult that the work is cut by the pin 12. The material of the work thuscut is discharged outside as burrs.

[0006] Hence, keeping the tool insertion depth into the work at anappropriate amount during the joining operation leads to an improvementof the quality of the joint. The insertion depth of the tool 10 into thework depends on a variety of factors, for example, a machining precisionof the work, a method of holding the work and a precision of the joiningapparatus itself. Establishing these factors within a precision of about0.05 mm is very difficult to achieve with the current level oftechnology. Although a desired machining precision may be realized byinvesting a sufficient time and cost, this leads to an increase in theoverall manufacturing cost and is practically difficult to realize.

[0007] To deal with such a problem, JP-11-226768A, for instance, shows amethod of controlling the insertion depth of the tool 10 into the workto be joined, which uses a laser displacement meter. FIG. 4 is asectional view showing an example construction of the joining apparatus.In this apparatus a table 27 is moved in the direction of X by a drivemotor 21. On the table 27, a work 26 to be joined is securely held by ajig not shown. A machine head 25 is moved in the direction of Z by ahead drive motor 22. The machine head 25 is supported by a ball thread29 and a guide not shown. The machine head 25 has mounted thereon a tool24 and a spindle motor 23 that drives the tool 24. The distance betweenthe machine head 25 and the surface 30 of the work to be joined ismeasured by the laser displacement meter 28 mounted on the machine head25. The distance measured is fed back and the head drive motor 22 iscontrolled to adjust the position of the machine head 25 so that thedistance between the machine head 25 and the surface 30 of the work iskept at a predetermined value at all times.

[0008] The position control using such a laser displacement meter is acommon measure also in the conventional arc welding and laser welding.It is common to perform the distance measurement by the laserdisplacement meter at a position offset to and slightly ahead of thetool. Thus, the distance between the machine head and the tool at themeasuring position of the laser displacement meter may slightly differfrom that measured near the tool. In the case of the friction stirwelding, the work to be joined is acted upon by a force of about 1000kgf from the tool. A problem therefore arises, for example, when a partof the work is slightly floated from the table. The laser displacementmeter beforehand reads this flowing and controls the machine head toraise it upward according to the measurement. When the tool passes thefloating position, the work is moved down by the force of the tool,increasing the distance between the tool and the work to slightly morethan an appropriate distance. Further, it should be noted that the laserdisplacement meter is designed to detect the state of the surface(surface position). The meter thus tends to be subject to influencesfrom, for instance, a change in radiation factor caused by smear of thesurface of the work or by oxidation of the work due to frictional heat.

[0009] JP-06-143015A teaches, in a cutting machine that performs cuttingwhile rotating a cutting tool by a main motor, adjusting a feed speed ofthe cutting tool to keep an electric current of the main motor at apredetermined value. But this reference does not show any particularrelationship of the feed speed with the friction stir welding.

[0010] JP-11-188517A discloses that, in a cutting machine that performscutting by rotating a cutting tool by a main motor, means is providedfor stopping feed means according to an amount of load detected by thefeed means. However, this reference is silent about any particularrelationship of the feed means in the friction stir welding.

BRIEF SUMMARY OF THE INVENTION

[0011] An object of the present invention is to provide a friction stirwelding apparatus and method and a processing apparatus and method, bothof which are not easily affected by deformations of a work beingprocessed.

[0012] The present invention features, in an aspect thereof, a frictionstir welding apparatus which joins members of a work by inserting arotating tool into the work and moving the rotating tool relative to thework, comprising a controller for controlling a relative distance in atool insertion direction between the tool and the work during thejoining operation or an insertion depth of the tool into the work sothat a load or electric current of a spindle motor for rotating the toolis within a predetermined range.

[0013] The invention resides also in a friction stir welding methodwhich features joining members of a work while controlling a relativedistance in a tool insertion direction between the tool and the workduring the joining operation or an insertion depth of the tool into thework so that a load or electric current of a spindle motor for rotatingthe tool is within a predetermined range.

[0014] The friction stir welding is a technique which is very simple inprinciple and can provide an excellent joint characteristic. Thistechnique, however, requires controlling the relative distance betweenthe tool and the work with a precision of about 0.05 mm at all times.This invention focuses on a heat balance in the friction stir welding.In the friction stir welding, a work done by the spindle motor inrotating the tool 10 constitutes a heat source.

[0015]FIG. 5 shows contact areas 31, 32 between the tool 10 and the workin the states of FIG. 2 and FIG. 3, respectively. As shown in FIG. 2 andFIG. 3, since the tool 10 is tilted at a predetermined angle θ to thework toward the rear side with respect to the moving direction, thecontact areas 31, 32 depend on the depth of insertion of the tool 10into the work. As described above, the work done by the spindle motor istransformed into frictional heat generated between the tool 10 and thework. When the revolution speed of the spindle motor is kept constant,the frictional heat generated depends on the contact area. Thefrictional heat diffuses into the work being processed. This heat raisesthe temperature of the work and thereby softens it, with the result thatthe work is stirred by the tool 10. When the contact area is large, theamount of frictional heat produced is large, and when the contact areais small, the amount of frictional heat is small. Therefore, to ensure astable joining operation at all times requires stabilizing the stirringof the work by the tool 10. That is, the load or electric current of thespindle motor, which constitutes the work done by the spindle motor orthe heat source, needs to be stabilized at all times.

[0016]FIG. 6 schematically shows a relationship between a tool insertiondepth and a spindle motor load (=work done by the spindle motor). In thefriction stir welding, the joint quality is influenced by the toolinsertion depth, and an appropriate tool insertion depth lies in acertain range. If the revolution speed of the spindle motor is constant,there is an appropriate range of the spindle load corresponding to anappropriate value of the tool insertion depth.

[0017] The invention features, in another aspect, in a friction stirwelding apparatus which joins members of a work by inserting a rotatingtool into the work and moving the rotating tool relative to the work,controlling a relative distance between the tool and the work during thejoining operation so that a load of the tool rotating spindle motor iswithin a predetermined range. The relative distance between the tool andthe work may be set by using the head drive motor 22 of FIG. 4, forexample. The load of the spindle motor may be electrically detected, forexample, from the spindle motor 23 of FIG. 4, and it is preferable toperform the detection by using an electric current.

[0018] A laser displacement meter or contact type displacement meterthat has conventionally been used may also be used additionally todetect the relative distance between the tool and the work or the amountof insertion of the tool into the work during the joining operation. Theload of the spindle motor depends on a temperature of the members of thework immediately before being joined together. For a work made ofaluminum or copper which has a good heat conductivity, for example, ifthe joining speed is significantly low, the frictional heat generatedbetween the tool and the work may be diffused, though very rarely,forward in the direction of tool advancement. When a temperature rise ofthe work in front of the tool caused by the diffused heat is more thanabout 50° C., the strength of the work in front of the tool (forexample, resistance to deformation at that temperature) deteriorates.Thus, if a work done by the spindle motor is constant, an excessive workis produced considering preheating due to the heat diffusion. Therefore,a laser displacement meter may be used as an auxiliary means. If thework to be processed has a shape consisting of an arbitrary curvedsurface, a line normal to an arbitrary curved surface may be detected byusing the laser displacement meter.

[0019] The invention further features, in another aspect, in a frictionstir welding method of joining members of a work by inserting a rotatingtool into the work and moving the rotating tool relative to the work,comprising the steps of rotating the tool at a constant speed whileinserting the rotating tool into the work at a constant insertion speed,when a predetermined load ratio or factor of a spindle motor relative toa maximum output for rotation of the tool or a predetermined insertiondepth of the tool into the work is reached, holding the rotating toolwhere it is for a predetermined duration, then moving the rotating toolin a joining direction at a constant joining speed to perform joining,and at the same time with the tool movement, controlling a relativedistance in a tool insertion direction between the tool and the workduring the joining operation or an insertion depth of the tool into thework so that a load factor or electric current of the spindle motor forrotating the tool is within a predetermined range.

[0020] The invention features, in still another aspect, in a frictionstir welding apparatus which joins members of a work by inserting arotating tool, rotated by a spindle motor, into the work and moving therotating tool relative to the work, comprising revolution speed settingmeans for setting a revolution speed of the tool, insertion speedsetting means for setting a constant insertion speed at which the toolrotating at a constant revolution speed is inserted into the work, loadfactor setting means for setting a load factor of the spindle motorrelative to a maximum tool rotation output or an insertion depth settingmeans for setting an insertion depth into the work, hold time settingmeans for setting a hold time during which the tool is held where it iswhen the load factor or insertion depth reaches the set value, joiningspeed setting means for setting a constant joining speed at which thetool is moved in a joining direction to join the members of the work,and a controller for controlling a relative distance in a tool insertiondirection between the tool and the work during the joining operation oran insertion depth of the tool into the work so that a load factor orelectric current of the spindle motor for rotating the tool is within apredetermined range.

[0021] The invention features, in still another aspect, in a processingapparatus or method which cuts or grinds a work by moving a rotatingcutter or grindstone relative to the work, comprising a controller forcontrolling a relative distance in a cutter or grindstone insertiondirection between the cutter or grindstone and the work during theprocessing operation or an insertion depth of the cutter or grindstoneinto the work so that a load factor or electric current of a spindlemotor for rotating the cutter or grindstone is within a predeterminedrange.

[0022] Further, the invention can also be applied similarly to aprocessing apparatus which cuts or grinds a work by inserting a rotatingcutter or grindstone, rotated by a spindle motor, into a work by a headdrive unit and moving the cutter or grindstone relative to the work.

[0023] The invention further features, in a further aspect, in aprocessing apparatus which cuts or grinds a work by inserting a rotatingcutter or grindstone, rotated by a spindle motor, into a work by a headdrive unit and moving the cutter or grindstone relative to the work,comprising revolution speed setting means for setting a revolution speedof the cutter or grindstone, insertion speed setting means for setting aconstant insertion speed at which the cutter or grindstone rotating at aconstant revolution speed is inserted into the work, load factor settingmeans for setting a load factor of the spindle motor relative to amaximum cutter or grindstone rotation output or an insertion depthsetting means for setting an insertion depth into the work, processingspeed setting means for setting a constant processing speed at which thecutter or grindstone is moved in a processing direction to process thework, and a controller for controlling a relative distance in a cutteror grindstone insertion direction between the cutter or grindstone andthe work during the processing operation or an insertion depth of thecutter or grindstone into the work so that a load factor or electriccurrent of the spindle motor for rotating the cutter or grindstone iswithin a predetermined range.

[0024] The invention features in a further aspect, in a processingmethod which cuts or grinds a work by moving a rotating cutter orgrindstone relative to the work, comprising the step of controlling arelative distance in a cutter or grindstone insertion direction betweenthe cutter or grindstone and the work during the processing operation oran insertion depth of the cutter or grindstone into the work so that aload of a spindle motor for rotating the cutter or grindstone is withina predetermined range.

[0025] The invention features, in a further aspect, in a processingmethod which cuts or grinds a work by moving a rotating cutter orgrindstone relative to the work, comprising the steps of inserting thecutter or grindstone rotating at a constant revolution speed into thework at a constant insertion speed, after a predetermined load factor ofa spindle motor relative to a maximum cutter or grindstone rotationoutput or a predetermined insertion depth into the work is reached,moving the cutter or grindstone in a processing direction to process thework, and at the same time with the movement, controlling a relativedistance in a cutter or grindstone insertion direction between thecutter or grindstone and the work during the processing operation or aninsertion depth of the cutter or grindstone into the work so that a loadfactor or electric current of the spindle motor for rotating the cutteror grindstone is within a predetermined range.

[0026] Other objects, features and advantages of the invention willbecome apparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0027]FIG. 1 is a block diagram showing the concept of a controller forthe friction stir welding apparatus of the invention.

[0028]FIG. 2 is an enlarged section view showing the detail of a tool inthe friction stir welding.

[0029]FIG. 3 is an enlarged section view showing the detail of a tool inthe friction stir welding.

[0030]FIG. 4 is a sectional view of the friction stir welding apparatusin which a control on the tool insertion depth is additionally made byusing a laser displacement meter.

[0031]FIG. 5 is a plan view showing contact areas between the tool andmembers of the work to be joined in the case of FIG. 2 and FIG. 3.

[0032]FIG. 6 is a diagram showing a basic concept of the invention,i.e., a relation between the tool insertion depth and the spindle motorload.

[0033]FIG. 7 is a sectional view of the friction stir welding apparatusof the invention.

[0034]FIG. 8 is a diagram showing changes over time of a control commandvalue, a work deformation and a spindle motor load factor in thefriction stir welding apparatus of the invention.

[0035]FIG. 9 is an external view of members joined together by thefriction stir welding of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0036] (Embodiment 1)

[0037]FIG. 1 is a block diagram of the friction stir welding apparatusshowing the concept of a relative position control on a tool and a workaccording to the invention. FIG. 7 is a cross section of the frictionstir welding apparatus with the controller of FIG. 1. In FIG. 1, an NCcontroller sets a spindle motor for rotating the tool and a head drivemotor for inserting the tool into the work to predetermined loadfactors, and with the input of a revolution speed of the tool and ajoining speed, joining is performed automatically. A programmablecontroller (PMC) monitors the load factor of the spindle motor andperforms a feedback control on the tool insertion depth.

[0038] That is, the NC controller and the PMC controller have revolutionspeed setting means for setting a revolution speed of the tool,insertion speed setting means for setting a constant speed at which thetool is inserted into the work while the tool is rotated at a constantspeed, load factor setting means for setting a load factor of thespindle motor relative to the maximum tool rotation output or aninsertion depth setting means for setting an insertion depth into thework, hold time setting means for setting a time duration for which thetool is held when the load factor or insertion depth reaches the presetvalue, and joining speed setting means for setting a joining speed atwhich the tool is moved in the joining direction to join members of thework. Further, these controllers control the relative distance in thetool insertion direction between the tool and the work during thejoining operation or the insertion depth of the tool into the work sothat the load factor or electric current of the spindle motor falls in apredetermined range.

[0039]FIG. 7 shows an apparatus of a type that is controlled by thecontroller of FIG. 1 and moves the table 27 left and right by the tabledrive motor 21 to form a linear joint in the X-axis direction. The work26 is held on the table 27 by a jig not shown. The work 26 comprises twomembers made of aluminum, each measuring 2000 mm long by 150 mm wide by5 mm thick, and these two members are placed in contact side by side ina direction perpendicular to the plane of the sheet. An iron plate 40 2mm thick is interposed at the center between the two members of the workto verify the function of this invention. As a result, the work 26 to bejoined rises about 2 mm at almost the central portion with respect tothe longitudinal direction.

[0040] The tool 24 is made from tool steel and has a shoulder diameterof 13 mm, a pin diameter of 6 mm and a pin length of 4.0 mm. The spindlemotor 23 for rotating the tool 24 has an output of 5 kW. The machinehead 25 mounting the tool 24 and the spindle motor 23 is supported bythe ball thread 29 and moved in the Z direction by a head drive motor27. These motors are controlled by the NC controller and the PMCcontroller not shown.

[0041]FIG. 8 shows changes over time of a spindle motor load ratio orfactor and a distance traveled by the machine head during operation.First, the tool 24 is rested 5 mm above the surface 30 of the work 26.The spindle motor 23 is operated at 1000 rpm and the head drive motor 22is also started to lower the machine head 25 at the rate of 5 mm/min.The lowering of the machine head 25 is controlled so as to stop thelowering of the tool 24 when the distance traveled by the machine head25 reaches 9.6 mm (=5.0+4.6 mm) or the load factor of the spindle motor23 (percentage of the current output with respect to the maximum output)is 73%.

[0042] At time (1) of FIG. 8, the spindle motor load factor was 73% andthe machine head 25 was stopped. The position of the machine head 25 inthis state was taken as a reference of a control command value (=0 mm).The tool 24 was held there for 20 seconds while rotating at a constantspeed. At this time, the spindle motor load factor slightly decreasedbut was not reflected on the control. After the tool was held for 20seconds, the table drive motor 21 was started to move the work 26relative to the tool 24 in the joining direction of X ((2) of FIG. 8).The table moving speed at this time was 400 mm/min. At the same timewhen starting the movement in the X direction, the machine head 25 wascontrolled vertically by the head drive motor 22 so that the load factorof the spindle motor 23 would be 68-71%. When the spindle motor loadfactor steps out of the band described above, the machine head 25 has tobe moved up or down at the speed of 6 mm/min. An almost central portionof the work 26 rises up about 2 mm. This concave configuration of thework 26 is also shown in FIG. 8.

[0043] At time (3) of FIG. 8, the process reaches the apex of the convexof the work. FIG. 8 clearly shows that the distance traveled by themachine head (control command value) perfectly follows the shape(deformation) of the work. The joining conditions and control parametersdescribed above are input through the NC controller, and a humaninterface is required only for input of the parameters into the NCdevice.

[0044]FIG. 9 compares an external view of a joint bead obtained byperforming the tool insertion depth control described above and anexternal view of a joint bead obtained with no tool insertion depthcontrol and by keeping the machine head 25 at the same position. Theposition of the apex of the convex as shown in FIG. 8 is indicated bythe same reference numeral (3). As shown in FIG. 9, when the control isperformed, the bead quality is stable, and on the other hand, when thecontrol is not performed, the tool cuts into the work significantly ataround (3), producing a substantial amount of burrs, as seen in thelower part of FIG. 9.

[0045] As described above, it is clear that performing the control onthe relative distance between the tool and the work or on the toolinsertion depth of the invention can produce an improved joint qualitywith no burrs and little depression. The invention can be implementedbasically with a relatively simple apparatus by adding software to theexisting NC controller.

[0046] (Embodiment 2)

[0047] The processing apparatus of this embodiment is used on aprecision processing apparatus such as a surface polisher, in which theinvention is applied in place of the tool of the Embodiment 1, andperforms rotation of a grindstone, its insertion into the work beingpolished and its movement in the processing direction in a way similarto the Embodiment 1. Further, the processing apparatus has a head drivedevice with a controller for controlling a relative distance between thegrindstone and the work being polished or an insertion depth of thegrindstone into the work so that the load factor or electric current ofa spindle motor falls in a preset range, as in the Embodiment 1.

[0048] More specifically, the processing apparatus with the controllerincludes revolution speed setting means for setting a revolution speedof a grindstone, insertion speed setting means for setting a constantspeed at which the grindstone is inserted into the work while thegrindstone is rotated at a constant speed, load factor setting means forsetting a load factor of the spindle motor relative to the maximumgrindstone rotation output or an insertion depth setting means forsetting an insertion depth into the work, processing speed setting meansfor setting a processing speed at which the grindstone is moved in theprocessing direction to process the work, and the controller forcontrolling the relative distance in the grindstone insertion directionbetween the grindstone and the work during operation or the insertiondepth of the grindstone into the work so that the load factor orelectric current of the spindle motor falls in a predetermined range.

[0049] With this construction, it is possible to keep the load factor orelectric current of the spindle motor for the grindstone within a presetrange at all times, thus allowing apparently smooth polishing. Thisembodiment is particularly advantageous for application to a mirrorsurface polisher with a curved surface.

[0050] According to the invention, the tool insertion depth into thework, the most important factor in the joint quality management of thefriction stir welding, can be kept constant at all times, achievingsignificant advantages of enabling a high precision control andautomation of the joining apparatus.

[0051] It will be further understood by those skilled in the art thatthe foregoing description has been made on the embodiments of theinvention and that various changes and modifications may be made in theinvention without departing from the sprit of the invention and thescope of the appended claims.

What is claimed is:
 1. A processing apparatus for cutting or grinding awork by moving a rotating cutter or grindstone relative to the work,comprising a controller for controlling a relative distance in a cutteror grindstone insertion direction between the cutter or grindstone andthe work during the processing operation or an insertion depth of thecutter or grindstone into the work so that a load or electric current ofa spindle motor for rotating the cutter or grindstone is within apredetermined range.
 2. A processing apparatus for cutting or grinding awork by inserting a rotating cutter or grindstone, rotated by a spindlemotor, into a work by a head drive unit and moving the cutter orgrindstone relative to the work, comprising a controller for controllinga relative distance in a cutter or grindstone insertion directionbetween the cutter or grindstone and the work during the processingoperation or an insertion depth of the cutter or grindstone into thework so that a load factor or electric current of the spindle motor iswithin a predetermined range.
 3. A processing apparatus for cutting orgrinding a work by inserting a rotating cutter or grindstone, rotated bya spindle motor, into a work by a head drive unit and moving the cutteror grindstone relative to the work, comprising: revolution speed settingmeans for setting a revolution speed of the cutter or grindstone;insertion speed setting means for setting a constant insertion speed atwhich the cutter or grindstone rotating at a constant revolution speedis inserted into the work; load factor setting means for setting a loadfactor of the spindle motor relative to a maximum cutter or grindstonerotation output or an insertion depth setting means for setting aninsertion depth into the work; and processing speed setting means forsetting a constant processing speed at which the cutter or grindstone ismoved in a processing direction to process the work.
 4. A processingapparatus for cutting or grinding a work by inserting a rotating cutteror grindstone, rotated by a spindle motor, into a work by a head driveunit and moving the cutter or grindstone relative to the work,comprising: revolution speed setting means for setting a revolutionspeed of the cutter or grindstone; insertion speed setting means forsetting a constant insertion speed at which the cutter or grindstonerotating at a constant revolution speed is inserted into the work; loadfactor setting means for setting a load factor of the spindle motorrelative to the maximum cutter or grindstone rotation output or aninsertion depth setting means for setting an insertion depth into thework; processing speed setting means for setting a constant processingspeed at which the cutter or grindstone is moved in a processingdirection to process the work; and a controller for controlling arelative distance in a cutter or grindstone insertion direction betweenthe cutter or grindstone and the work during the processing operation oran insertion depth of the cutter or grindstone into the work so that aload factor or electric current of the spindle motor for rotating thecutter or grindstone is within a predetermined range.
 5. A processingmethod for cutting or grinding a work by moving a rotating cutter orgrindstone relative to the work, comprising the step of controlling arelative distance in a cutter or grindstone insertion direction betweenthe cutter or grindstone and the work during the processing operation oran insertion depth of the cutter or grindstone into the work so that aload factor or electric current of a spindle motor for rotating thecutter or grindstone is within a predetermined range.
 6. A processingmethod of cutting or grinding a work by moving a rotating cutter orgrindstone relative to the work, comprising the steps of: inserting thecutter or grindstone rotating at a constant revolution speed into thework at a constant insertion speed; and after a predetermined loadfactor of a spindle motor relative to a maximum cutter or grindstonerotation output or a predetermined insertion depth into the work isreached, moving the cutter or grindstone in a processing direction toprocess the work.
 7. A processing method of cutting or grinding a workby moving a rotating cutter or grindstone relative to the work,comprising the steps of: inserting the cutter or grindstone rotating ata constant revolution speed into the work at a constant insertion speed;after a predetermined load factor of a spindle motor relative to amaximum cutter or grindstone rotation output or a predeterminedinsertion depth into the work is reached, moving the cutter orgrindstone in a processing direction to process the work; and at thesame time controlling a relative distance in a cutter or grindstoneinsertion direction between the cutter or grindstone and the work duringthe processing operation or an insertion depth of the cutter orgrindstone into the work so that a load factor or electric current ofthe spindle motor for rotating the cutter or grindstone is within apredetermined range.